Study: Caffeinated Energy Shots Don't Improve 5-K Time

Caffeine has repeatedly been shown[4] to improve endurance performance in research trials. That being the case, then downing convenient, caffeinated "energy shots" should automatically mean better race times, right?

Not so fast, according to a small study[5] published in the journal Nutrients. It found no improvement in performance when highly trained runners consumed two popular commercially available energy shots an hour before an all-out 5-K.

Six runners with an average 5-K best of 15:00 did 5-K time trials on a treadmill on three occasions: after drinking a 2-ounce Red Bull Energy Shot, a 2-ounce Guayaki Yerba Mate shot, or a 2-ounce drink containing no caffeine but made to taste like Red Bull. The researchers chose that volume of drink to better mimic what runners might do in the real world, given that a 2-ounce serving is a commonly available size for energy shots.

The Red Bull shot contained 80 milligrams of caffeine, the Yerba Mate shot contained 140 milligrams of caffeine, and the placebo shot contained 0 milligrams of caffeine. By way of comparison, an 8-ounce cup of coffee contains between 100 and 200 milligrams of caffeine.

Fifty minutes after the runners drank the shots, they warmed up for 10 minutes, rested for 5 minutes, and then ran a 5-K as fast as they could on a treadmill. Their average times were slower after drinking the Red Bull (17:33) and Yerba Mate (17:51) than after drinking the placebo (17:26).

As the researchers note, previous studies demonstrating a performance boost from caffeine used more science-geek (our term, not theirs) means of determining how much caffeine to give exercisers; milligrams of caffeine per kilogram of body weight is the most common measurement. A strength of this study is that it provided caffeine in the amounts most people are going to more often encounter.

It's also worth bearing in mind that many studies on caffeine and endurance performance look at extending duration, not improving times at a set distance. And many studies are done on cyclists, who can usually work at higher intensities than runners without having stomach problems.

Evidence is still very much in caffeine's favor as helpful to runners. But, as this study reminds, that's different than saying that every run will be faster if preceded by caffeine.